2001 Jetta 2.0 turns over no star/no spark

My buddy and I have replaced the crankshaft sensor, camshaft sensor, speed sensor, ignition switch, ignition coil, fuel pump relays, and lastly, I replaced the MAF sensor by pulling a 99 MAF sensor from a junker. The day before I replaced the MAF sensor, the car started every time and as it should. The exact moment I tried to start this Jetta, after replacing the MAF sensor, it will not start INTERMITTENTLY. Sometimes it gets spark after trying for minutes and backfires LOUDLY and sometimes it doesn't, and sometimes it starts right up.

WHAT IS HAPPENING. Please, I am at my wits end and this is my wife's only car for work and to drive my daughter and her around. Please, someone help diagnose this.

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